Gelled water has been used as a fire suppressant, primarily on an experimental basis, since as early as the 1960s. Physically, gelled water varies from viscous, but readily flowable water, to semi-solid gelatinous materials that adhere to vertical surfaces. The physical characteristics of the gelled water used to suppress fire are varied dependent on the mode of application and the strategy being employed. Early gelling agents were granular or powdered and had to be pre-blended with water to form the gelled water to be applied. These gelling agents are typically referred to as super absorbent polymers or “SAPs”. Gelled water is superior to liquid water in many fire suppressant applications because it adheres to fuels and surfaces much better than liquid water, which readily flows off the materials to be protected.
The use of early products was essentially discontinued because control of admixing the granular or powdered super absorbent polymers with water was difficult and time consuming and because their performance was greatly influenced by water hardness ions. More recently, concentrated liquid super absorbent polymers have been introduced as fire suppressant gels. These concentrated liquid products can be readily proportioned with water to form the viscous characteristics of the gel that are desired.
Super absorbent polymers (SAPs) are water soluble polymers than can absorb and retain extremely large volumes of water relative to their own mass. Currently available SAP type products generally consist of sodium and/or potassium salts of polyacrylic acid, polyacrylamide, or mixtures thereof suspended in suitable non-solvent liquids. These products can be easily proportioned with water to overcome prior mixing difficulties. However, they continue to suffer from the impact of water hardness ions present in the mix water used to prepare the gelled water.